Multiplex telegraphy



W. M. BRUCE, JR

MULTIPLEX TELEGRAPH! flSheets-Sheet 1 Filed May 2, 1921 3 Sheets-Shet 2 Filed May 2, 1921 awue-mtoz Patented Oct. 20, 1925.-

UNITED STATES WILLIAI I. BRUCE, JR., OF SPRINGFIELD, OHIO.

IULTIPLEX TELEGRAPH.-

Applicatlon filed Kay 2,

To all whom it may concern:

Be it known that I, WILLIAM M. BRUCE, Jr., a citizen of the United States, residing at Springfield, in the county of-Clark and State of Ohio, have invented certain new and useful Improvements in Multiplex Telegraphy, of which the following is a specification.

My invention relates to multiplex telegraphy and has for its object transmisison ofa plurality of telegraphic messages over a single circuit. In accomplishing the above results, I make use of high frequency currents or electro-magnetic waves preferabl in low frequency groups in connection wit 1 apparatus electrically tuned to the hi h frequencies and mechanically tuned to t e low frequency groups.

Multiplex telephony and telegraphy is at the present time practiced'in connection with electro-magnetic Waves or oscillations of high frequency, guided by wires, in which different high frequencies are used as carriers for different messages, with selective apparatus to select the different carriers or carrier waves and for reducing them to audibility at the receiving station. By this method a different message for each fre'-.

quency may be transmitted when the frequencies vary from each other in a proper degree.

With my improved, method of multiplex telegraphy, I am able to employ electronia netic waves or oscillations of a si le hig frequency for transmitting several differentmessages so that the number of messages which may be safely transmitted by a single conductor or circuit without interference under the present practice may be multiplied as manytimes as the number of p messages which can be impressed upon and transmitted by the electro-magnetic waves or oscillations of one frequency can be-successfully applied.

As inted out in my pending ap lication No. 44 2968 I have found it practicable to mechanicall tune a receiving apparatus such as a movab e coil so that it will respond to and vibrate with certain cunent frequencies and will not respond to other frequencies. Justwithin what range it is 'bleto eflect this mechanicallymtun' not as yet been determined, t I ve demonstrated that it is practicable to efiect this mechanically tuning with a range of from 1821. Serial No. 488,015.

80 to 300 cycles or vibrations and within this range to secure eight different periods at which reception can take lace without interference. In other wor s, by starting at 80 cycles or vibrations per second and varying; the periods by 20 cycles, I secure 12 periods between 80 and 300, differing from each other by 20 cycles or vibrations per second at which "these mechanically tuned receiving devices will respond to their respective periods or vibrations and not respond .to the other periods or vibrations.

Under these conditions it will be readily apparent that one electro-magnetic wave frequency of say 20,000 cycles r second can be made to transmit 12 di erent messages when the oscillations at this frequenc are broken upinto 12 different groups, eac

group of which will difl'er from the other groups by 20 or more frequencies or interrupt 1ons per second and inasmuch as it is possible to employ high frequency waves which difier from each other by a comparatively small percent without interference, the number of messages which may be transnitted over a sin le conductor or circuit, it will be seen, is united only by the' number of diiferent electro-magnetic wave frequencies which could be employed or in pract1cal application by the amount of space necessary to equip the pro r trans mitting and receiving stations. nder some conditions I have found it desirable to employ an auxiliary circuit for the receiving apparatus which may be electrically tuned to the low frequency groups to operate the receivers.

In the drawings which form a part of this specification: Fig. is. a diagrammatic view illustratmg a simple plan for ea in out my improved method of telegrap y m which four transmitting stations and four receiving stations are applied to the same circuit, these stations being shown in pairs withone high frequency for each pair and a difierent interrupted or group frequency for each sta-' tion of each pair, the receiving stations being similarly arranged.

In Fig. 2 I have illustrated in diagrammatic form circuits and apparatus for transmittin four in each direction over a Bing e conductor. In this case four different high frequencies are indicated and two difi'enent group frequencies, that is, one

\ will correspo group frequency for messages transmitted in one direction and another group frequency for messages in the other direction. Fig. 3 is a dia rammatic view showing modifications of the sending and receiving devices. a

In carrying out my invention I make use of an welLknown apparatus now to be ob-. taine for producing t e necessary high frequency electro-magneti'c waves or oscillatrons and as such devices are now in common use and on the market, I have not attempted to show them. These high frequency waves or oscillations will be applied to the circuit in any desired way preferably in the manner as now applied to wireless circuits which circuit may be. tuned in resonanc therewith in the usual way. For each of he high fr uency circuits thus employed I insert at t e transmitting station as man circuit breakers as is desired, within the imits of the tuning of the receiving devices, to break up these fr uency waves into low frequency groups 0 the desired periodto correspond to the tuning of the receiving devices and upon these grou freuencies,"I impress .the telegraphic signals t rough any suitable telegraphic transmitter.

At the receivin end, I employ any well known method 0 receiving and securing resonance with-the high frequency waves. preferably through the vacuum tube detector and in the plate circuit of this receiving agency of a threeelectrode device. I place my mechanically tuned receiving device preferably in the form of a relay and where such a rectifying detector is used, I interpose between the detector and relay, a-transormer in order to secure the necessary current alternations tooperate the tuned vibrating receiving device. When this tuned vibratingreceiving device isa relay it may be ar d to control a local circuit 0 ratin an ordinary sounder or any other isiitabl translating device. I

Referring to Fig. 1 of the drawings at the left end of the sheet is shown a transmitting station A and at the right end a receiving a station B. The transmitting station is ar-- ranged to transmit' and the receiving station is arranged to receive four different messages at the same time. For the urpose of illustration I have shown'two of t e smding circuits operating with one high frequency .th

say 20,000 cycles and the other two it anot er 111%! frequency, say 30,000 cycles. Each of t ese circuits are provided with an interrupter to break up the high 'frequenc oscillations into groups of a frequency whic nd to the mechanical tun of the receiving device. I. have indicat in the drawings one of the circuits of 20,000 frequencies interrupted eighty times per second, the same being true of the circuits using the thirty thousand frequencies. An ordinary telegraph-key or other transmitter provided in each circuit for interru ting the circuit by long and short interv'a s corresponding to dots and dashes. The equipment for supplying high frequency currents may be'such as is now well known for supplfiing these high frequency currents or osc' ations in wireless practice.

I In the drawings the respective circuits are numbered 1, 2, 3, and 4 each of which is provided with the usual variable condenser 0 c 0, and c and the variable coil a a a and a. Some form of generator for pro .maries 12 p p and p of transformers,

the secondaries s s s ands of which are in the respective circuits 1, 2, 3, and 4 which would correspond to the aerial circuits in a wireless system. The interrupters which break up the high frequency waves or oscillations into groups of the desired frequency as for instance 80 and 100 frequencies per second for the respective circuits are shown at b b b and b. The transmitting devices which may be of any desired type for transmitting the signals such, as dots and dashes in the ordinary Morsecode are indicated at (Z d d, and d.

At the receiving station thecircuits 5, 6, 7, 8 correspond to the usual aerial circuitsof a wirelessstation each of which is preferably grounded lthrough the usual variable condensers c, 0, 0" and 0 and connected to the detectors e e c and 0 preferably of the three electrode vacuum tube type, this connection being established in the usualway through coupling coils t, t, t", t. In the plate circuits f, f, f and f of each of these detectors, I insert the primaries of transformers h, it, h and h, the secondary circuit of each of which includes a vibrating coil receiving device 1, r 1? and r. Each of these receivers are .mechanicall .tuned in the'manner explained. in my .pen ing application to respond tofla givennumber of vibrations. In the present case the receivers 2' and 1' will be tuned to eighty vibrations and the receivers r and r to 100 vibrations .to correspond to the transmitting circuits 1, 3 and 2, 4. These receivers may be in the nature of relays or recorders. If recorders, ay would preferably beof the siphon type adapted by their vibrations to record long an short intervals of vibration corresponding to the dots and dashes at the transmitters as shown in the pending application above referred to. If used as relays they would. 'be adapted to control a local circuit through which any suitable translating device could be-operated. In the drawings I have shown each of second and theother, one hundred times per these vibrating receiving devices acting and break circuits which include the usual sounders or other translating devices m m m and m.

,In Fi 2 I have illustrated four transmit-- ting an four receiving circuits at two stations. v In this diagram the transmitting mechanism is not shown in detail but is indicated in diagram at the top of'the sheet. At that station at the left of the sheet I have indicated four transmitting sets 9, 10, 11, 12 and at the station at the right of the sheet four similar transmitting sets'13, 14, 15 and 16. Each of these sets will be supplied with apparatus similar to that shown at stat1on A 1n Fig. 1 which will supply the high frequency currents of different cycles each broken up into groups of a desired frequency. In this case I have illustrated the high frequency currents of 20,000, 30,0 00, 40,000 and 50,000 for the respective circuits. For each of the transmitting stations'at the left of the sheet I have indicated; group frequencies of 100 and, for those: at the ri ht of'the sheet group frequef ies of 200. T e receivers for these 'variousicircuits are the same as described with j reference to Fig. 1, there being a vacuum tube detector,

for each of the'receivin circuits and a vibrating receiver mechanically tuned to the required frequency; those receivers at the station-at the left being tuned to 200 cycles to correspond with the group frequencies of the'sending circuits of thestations at the right'and these receivers'in the station at the right being tuned to 100 cycles to correspond "0 the group frequencies of the sending stations at the left. I v g It will be understood in the operation of this system that the incoming circuits for these receiving stations will be electrically tuned in the usual'way to the high frequency waves or oscillations which will be impressed uponthe respective detectors thus producing unidirectional currents in the plate circuits of the detectors in groups corresponding to the frequency of the-interruption at the sending station and that the receiving devices being mechanically tuned to the res ctive grou frequencies will respond to t ose particu ar frequencies.

In the lay-out shown in Fig. 2 instead of using high frequency currents of different frequencies for the ei ht difl'erent circuits,

that is,four in each irection, I could employ high frequency currents of the same frequencies with interrupters for the different circuits adapted to interrupt these high frequency currents at the low frequencies of say from to 220 or additional circuiterould be provided with the same group frequencies for each of the'high fr equency currents indicated, that is, instead of I the eight circuits herein illustrated (four i ach direction) with the same four hi close, it will be seen that the number of circuits which can be impressed upon a single conductor has a very wide rang Where the high frequency currents such as herein described are used in connection with low frequency groups, multiplex teleg- As the limits raphy can be effected over any of the ordi nary circuits now employed for telephonic or telegraphic purposes without disturbing the regular circuits now in use as the high frequencies being above audibility will not interfere with telephonic conversation nor would they interfere with the ordinary battery transmission for telegraphic purposes.

I have found it advantageous in some cases to employ at the receiving end an additional circuit in connection with thedetector circuit which will be separately tuned in electrical resonance with thevparticular low frequency group, that is to be received by that circuit'and place the me-' circuit. In this case, the usual detector circuit will be tuned to the high frequency chanically tuned receiver directly in this waves and the secondary circuit will be tuned to the low frequenc groups; This has special advantages w ere the circuit wires or conductors. I

Where this auxiliary tuning is effected-for inay be subjected to outside influences, and

it has its advantages whether employed in connection with conductors or guide wires: with a high frequency current or employed se,

with radio transmission without the use of no the low frequencies, an ordinary telephone receiver may be substituted for themechani cal tuneddevice as shown at w in Fi can-=- which the range of low f quencies is veryfl materially increased sinc such a receiver will respond to practically all frequencies within the range of audibility.

Having thus described my invention, I claim 1. In a system of multiplex telegraphy, means at a sending station for sup y current of different high frequenci s a i n different circuits connected to a single con- -duct0r and means for producing comparatively low frequency groups high frequency currents in each of said circuits and impressing upon these groups signals c'orresplonding to dots and dashes in connection wit apparatus at a receiving station comprising an electrically tuned device for eachhigh frequency current in resonance therewith, and a separate receiving device for each group comprising a vibrating coil me chanically tuned to the low frequency groups which receiving devices are connected 1n multiple to said conductor.

2. The method of transmitting and receiving signals which consists in impressing upon a single conductor different high fre quency currents from different circuits, one for each high frequency, varying these high frequency currents into groups of comparatively low frequency and impressing the signals upon the low frequency groups selecting the high frequency currents at a receiving station by vacuum tubes electrically tuned to the respective frequencies and selecting the low frequency groups by vibrating coil receiving devices mechanically tuned to said groups.

3. In a system for multiplex telegraphy, means at a sending station for supplying to a single conductor high frequency currents in comparatively low frequency groups and impressing upon these groups the signals to be transmitted in connection with apparatus at a receiving station com rising vacuum tube detectors, one for eac high frequency and in resonance therewith, and a separate receiving device for each group connected in multiple with said detector and comprising a vibrating coil mechanically tuned to the low frequency groups and re-' spending to the signals impressed thereon. 4. In a system V of multiplex telegraphy, means for supplyingto a single conductor currents of different high frequencies in groups of comparatively low frequency and impressing upon these groups signals to transmitted, a vacuum tube detector at a receiving station for each' different .set of signals to be received and adapted to select a particular high frequency, and a secondar circuit including a vibrating coil recelver mechanically tuned to frequencies of a particular group and to translate the Signals carried thereby. v

5. In a system of multiplex telegraphy, a plurality of sending devices comprising currents varying each of these big means for supplying different high frequency currents, and means connected with each of these devices for producing comaratively low frequency groups of hi h requency currents, and separate means or impressing on the low frequency oups sig: nals corresponding to dots and, ashes and impressing the various low frequency roups of igh frequency upon a single conductor, receiving devices comprising vacuum tube detectors in resonance with the high frequency currents and mechanically tuned'vibrating coil receiving devices mechanically tuned to the low frequency groups at a receiving station and connected in multiple to said conductor and adapted to respond to the different frequencies and to translate "thedifierent signals impressed on said different frequencies.- I

6. In a system of multiplex telegraphy, the combination at a sendin station, means for supplying currents of di erent high frequen'cies to different circuits and in each of said circuits for producing comparatively low frequency groups of said high frequency currents and for impressing signals on said low frequency groups in combination with a vacuum tube detector at a receiving station and a transformer in the plate circuit of said tube, a mechanically tuned vibrating coil relay connected to said transformer and a translating device operated by said relay for the purpose set forth. i 7 The method of transmitting and receiving signals which consist in impressing upon a single conductor different high fre uepcy reuency currents into groups of comparab tively low frequency and impressing different signals upon the low frequency roups of each of said high frequencies ecting the different high frequency currents at a receiving station b electrically tuning and selecting the low requency groups 0 each hi h frequency by mechanically tuning.

i1 testimony whereof,.I have hereunto set my hand this 28th day ,of April, 1921.

WILLIAM M. BRiicE, JR 

